The invention relates to an airbag apparatus for a vehicle, and more particularly to an airbag apparatus for a passenger seat.
In Japanese Patent Application Laid-Open publication H8-268213, there is a disclosure of an airbag apparatus.
In the above-noted airbag apparatus, an airbag module is installed in an instrument panel disposed below a front window. The airbag module houses within it an airbag folded up inside a case having an aperture blocked by a cover which can be burst open, and an inflator for ejecting gas into the airbag. When a collision occurs, the gas is ejected into the airbag, thereby causing the airbag to burst the cover open, and enabling it to deploy within the passenger compartment of the vehicle.
According to an investigation made by the present inventor, in an airbag apparatus, in order to achieve reliable bursting open of the cover by the airbag, it is preferable that a high-output inflator is used, so as to raise the pressure inside the airbag as much as possible.
From the standpoint of restraining an occupant of the vehicle with the airbag, it is preferable that the internal pressure of the airbag is adjusted so as to achieve an appropriate condition of restraint of a passenger.
Therefore, one method that can be envisioned is forming a vent hole that allows appropriate escape of the gas inside the airbag from therewithin, thereby adjusting the internal pressure.
If a vent hole is formed in the airbag so as to escape the internal pressure of the airbag, however, merely forming a hole in the base cloth of the airbag could result in the vent hole being torn by the strong force of the ejected gas.
For this reason, there is a need to use a strong material, for example, and to provide a special strong reinforcement at the edge part of the vent hole. This configuration, however, is not desirable because it causes complicated construction of the airbag.
Accordingly, in view of the above-noted analysis, it is an object of the present invention to provide an airbag apparatus for a vehicle which does not rely solely on a vent hole in enabling adjustment of the internal pressure of the airbag.
To achieve the above object, an airbag apparatus according to the present invention has a case with an opening that is blocked by a cover that can be burst open, a folded-up airbag installed within the case, and an inflator for ejecting gas into the airbag installed within the case, via a gas guide port. The airbag, which is expanded by the gas ejected from the inflator causes the cover to burst open, enabling its deployment within the passenger compartment of the vehicle. The airbag is branched from the gas guide port to a small-capacity sub-expansion part and a large-capacity main expansion part. Here, the sub-expansion part is disposed at the front window panel side of the front portion of the passenger compartment, and the main expansion part is disposed at the passenger side of the passenger compartment.
According to the above-noted configuration, preferably adjusting the internal airbag pressure and using a relatively small pressure, it is possible that the entire airbag is caused to deploy quickly in a desired direction.